<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>:before :after</title>
    <style>
        p:before{
            content: 'HHH';
        }
        p:after{
            content: 'ddd';
        }
    </style>
</head>
<body>
    <p>ello world</p>
</body>
</html>